This invention relates generally to signal transmitting systems and more particularly to a system for transmitting data from a control location to a remote display location using a minimum number of conductors.
Multiple character displays such as seven-segment alphanumeric displays are widely used. Such a display may comprise light-emitting diodes (LED), liquid crystal display segments (LCD) or any other multiple character or multiple segment type of display. While the invention is useful with any multiple character display, the disclosure will be facilitated by specific reference to seven-segment alphanumeric displays.
In such seven-segment displays, various alphabetic or numeric characters may be formed by selectively energizing appropriate combinations of the segments. Accordingly, in order to selectively energize any given combination of segments, seven separate transmission lines or conductors are generally required to separately energize and de-energize each of these seven segments, in addition to common positive voltage supply and common ground conductors. Hence, for a two-character alphanumeric display, at least sixteen independent data lines or conductors are needed, including the common voltage supply and ground lines. As the number of seven-segment display elements increases, the number of conductors required increases accordingly.
It will be apparent that the provision of cables and connectors for interconnecting such displays with remotely located control or data generating devices becomes complex and expensive as the number of conductors required increases. The prior art has heretofore attempted to decrease the number of conductors required by utilizing multiplexing and de-multiplexing and other serial to parallel and parallel to serial encoding and decoding techniques. However, such techniques generally require the use of relatively expensive integrated circuit components. Hence, in applications where a plurality of remote control or data generating stations must be coupled with a single centrally located display location, a corresponding plurality of expensive decoding and encoding integrated circuit components must be utilized.